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package result
import (
"reflect"
"strings"
"sync"
"unicode"
"unicode/utf8"
"codeberg.org/gruf/go-byteutil"
"codeberg.org/gruf/go-mangler"
)
// structKeys provides convience methods for a list
// of structKey field combinations used for cache keys.
type structKeys []structKey
// get fetches the structKey info for given lookup name (else, panics).
func (sk structKeys) get(name string) *structKey {
for i := range sk {
if sk[i].name == name {
return &sk[i]
}
}
panic("unknown lookup: \"" + name + "\"")
}
// generate will calculate and produce a slice of cache keys the given value
// can be stored under in the, as determined by receiving struct keys.
func (sk structKeys) generate(a any) []cachedKey {
var keys []cachedKey
// Get reflected value in order
// to access the struct fields
v := reflect.ValueOf(a)
// Iteratively deref pointer value
for v.Kind() == reflect.Pointer {
if v.IsNil() {
panic("nil ptr")
}
v = v.Elem()
}
// Acquire byte buffer
buf := bufpool.Get().(*byteutil.Buffer)
defer bufpool.Put(buf)
for i := range sk {
// Reset buffer
buf.B = buf.B[:0]
// Append each field value to buffer.
for _, idx := range sk[i].fields {
fv := v.Field(idx)
fi := fv.Interface()
buf.B = mangler.Append(buf.B, fi)
buf.B = append(buf.B, '.')
}
// Drop last '.'
buf.Truncate(1)
// Don't generate keys for zero values
if allowZero := sk[i].zero == ""; // nocollapse
!allowZero && buf.String() == sk[i].zero {
continue
}
// Append new cached key to slice
keys = append(keys, cachedKey{
key: &sk[i],
value: string(buf.B), // copy
})
}
return keys
}
// cachedKey represents an actual cached key.
type cachedKey struct {
// key is a reference to the structKey this
// cacheKey is representing. This is a shared
// reference and as such only the structKey.pkeys
// lookup map is expecting to be modified.
key *structKey
// value is the actual string representing
// this cache key for hashmap lookups.
value string
}
// structKey represents a list of struct fields
// encompassing a single cache key, the string name
// of the lookup, the lookup map to primary cache
// keys, and the key's possible zero value string.
type structKey struct {
// name is the provided cache lookup name for
// this particular struct key, consisting of
// period ('.') separated struct field names.
name string
// zero is the possible zero value for this key.
// if set, this will _always_ be non-empty, as
// the mangled cache key will never be empty.
//
// i.e. zero = "" --> allow zero value keys
// zero != "" --> don't allow zero value keys
zero string
// fields is a slice of runtime struct field
// indices, of the fields encompassed by this key.
fields []int
// pkeys is a lookup of stored struct key values
// to the primary cache lookup key (int64).
pkeys map[string]int64
}
// genStructKey will generate a structKey{} information object for user-given lookup
// key information, and the receiving generic paramter's type information. Panics on error.
func genStructKey(lk Lookup, t reflect.Type) structKey {
var zeros []any
// Split dot-separated lookup to get
// the individual struct field names
names := strings.Split(lk.Name, ".")
if len(names) == 0 {
panic("no key fields specified")
}
// Pre-allocate slice of expected length
fields := make([]int, len(names))
for i, name := range names {
// Get field info for given name
ft, ok := t.FieldByName(name)
if !ok {
panic("no field found for name: \"" + name + "\"")
}
// Check field is usable
if !isExported(name) {
panic("field must be exported")
}
// Set the runtime field index
fields[i] = ft.Index[0]
// Allocate new instance of field
v := reflect.New(ft.Type)
v = v.Elem()
if !lk.AllowZero {
// Append the zero value interface
zeros = append(zeros, v.Interface())
}
}
var zvalue string
if len(zeros) > 0 {
// Generate zero value string
zvalue = genKey(zeros...)
}
return structKey{
name: lk.Name,
zero: zvalue,
fields: fields,
pkeys: make(map[string]int64),
}
}
// genKey generates a cache key for given key values.
func genKey(parts ...any) string {
if len(parts) == 0 {
// Panic to prevent annoying usecase
// where user forgets to pass lookup
// and instead only passes a key part,
// e.g. cache.Get("key")
// which then always returns false.
panic("no key parts provided")
}
// Acquire buffer and reset
buf := bufpool.Get().(*byteutil.Buffer)
defer bufpool.Put(buf)
buf.Reset()
// Encode each key part
for _, part := range parts {
buf.B = mangler.Append(buf.B, part)
buf.B = append(buf.B, '.')
}
// Drop last '.'
buf.Truncate(1)
// Return string copy
return string(buf.B)
}
// isExported checks whether function name is exported.
func isExported(fnName string) bool {
r, _ := utf8.DecodeRuneInString(fnName)
return unicode.IsUpper(r)
}
// bufpool provides a memory pool of byte
// buffers use when encoding key types.
var bufpool = sync.Pool{
New: func() any {
return &byteutil.Buffer{B: make([]byte, 0, 512)}
},
}
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